This invention relates in general to an arrangement for measuring the rate of flow of a gaseous or liquid medium through a housing and, in particular to an arrangement for measuring the volume of air flowing through the intake pipe of an internal combustion engine.
In German Patent Publication DE-OS No. 22 46 546, an air measuring means is known for a fuel supply system of a mixture compressing, spark ignition, internal-combustion engine having an air-intake pipe in which the air measuring means is arranged. In correspondance to the amount of air flowing through the intake pipe, the air measuring means is moved against a restoring force. The displacement of said air measuring means represents a measurement of the amount of air taken in. The air measuring means, on one side, is disposed so that it can be rotated around a fixed bearing shaft arranged transversely in the air intake pipe and takes the form of an air flap transversely arranged in the air intake pipe. The air flap is swivelled against the force of a restoring spring. A particular problem with this arrangement has been the bearing arrangement for the air flap. In order to achieve an exact transmission of information, this bearing would have to be almost without friction. However, this can be achieved only by means of considerable manufacturing costs and results in a significant susceptibility to momentary disturbances.
It is an objective of this invention to provide an arrangement of the above type for measuring the rate of flow of a gaseous or liquid medium through a housing, which can be manufactured by simple means, is not susceptible to disturbances and is able to precisely record the measured values.
The above and other objects are attained in an arrangement for measuring flow of a fluid medium through a housing, comprising air measuring means arranged in the housing, the measuring means being movable in response to a flow of medium in the housing. Displacement of the measuring means is representative of the amount of medium flowing through the housing. The arrangement also comprises a control valve, arranged in a control pipe adjacent to the housing, for metering a control medium in proportion to the amount of medium flowing through the housing. The control valve has a movable part which interacts with and is responsive to the displacement of the air measuring means. The air measuring means comprises a leaf spring pivotably mounted adjacent a first wall of the housing at an upstream end of the leaf spring, and having a downstream end which rests against a second wall of the housing when the measuring means is in a closed position. In a preferred embodiment, the leaf spring is concavely shaped relative to the flow direction of the medium. In an especially preferred embodiment, the leaf spring has a wave or step-shaped deformation extending transversely to the flow direction of the medium.
The measuring means further includes a shaft body disposed transversely to the flow direction of the medium and rotatably mounted to the housing. The shaft body includes adjustment means for adjusting the measuring means in the flow direction of the medium.
In a preferred embodiment, the leaf spring is rigidly attached to a support plate. The support plate can be adjusted by the adjustment means of the shaft body in the flow direction of the medium. The support plate has guide bars which are guided in guiding slots in the shaft body, and an adjustment stop which interacts with the adjustment means of the shaft body. The adjustment means of the shaft body preferably comprises a screw arrangement connecting the shaft body and the adjustment stop. The screw arrangement comprises a screw and a coaxially arranged spring. In the illustrated embodiment of the invention, the support plate interacts with the movable part of the control valve. The leaf spring is attached to the support plate in the area of the shaft body.
The preferred embodiment of the invention further comprises a setting device for adjusting the support plate vertically with respect to a flow direction of the medium. The setting device comprises a threaded connection between the support plate and the housing. The threaded connection includes a screw bolt and a compression spring coaxially arranged on the screw bolt between a head of the screw bolt and the housing. The setting device is preferably connected to the support plate by a spring.
In a preferred embodiment of the invention, the leaf spring has at least one cross-section reducing recess which can be closed by an elastic covering fastened on one side to a side of the leaf spring which faces the approaching medium.
Another preferred embodiment of the invention includes a damping device which comprises a cylinder closed on one end and equipped with a spring loaded return valve. The cylinder is fastened to the housing at its open end. A damping ball is guided within the cylinder and is connected by a connecting rod to an elastic joint fastened to the leaf spring. The damping device includes a connecting pipe which connects the space in the cylinder located above the damping ball with the space in the cylinder located below the damping ball. A throttle is preferably disposed in the connecting pipe to further control the damping function. The connecting pipe is connected at a point downstream from the throttle with the space of the cylinder located above the damping ball by a short circuit line in which the spring loaded return valve is located. This arrangement reduces the damping in one direction.
The leaf spring is preferably made from a bimetal strip.
Other features of the invention include a contoured protruberance located in the housing and acted upon by the medium. The contoured protruberance is located on the housing in the area of the downstream end of the leaf spring. In a preferred embodiment, the support plate has a wave or step-shaped deformation extending transversely to the flow direction of the medium.
The arrangement according to the invention can be used for liquids and for gases and can function in any installed position. Because of the small mass of the leaf spring, a rapid recording of measured values is possible. The arrangement requires little space and has a low weight. The basic adjustment and the characteristic curve of the arrangement can be modified easily and flow losses are low.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.